The ultimate objective of the proposed project is the elucidation at the molecular level of those processes involved in the transport and control of transport of materials across the cell membrane. Two timely and important questions in the field of membrane transport today are: a) the role of ion fluxes and ion gradients in the transport of organic substrates and b) the existence of functional carriers (facilitated diffusion) after the energy of an active transport has been eliminated. It is the aim of this project to investigate these questions. I intend to extend these studies to animal cell membranes, employing membrane vesicles derived by fragmentation or endocytotic procedures to obtain vesicles of both orientations. The transport across the membrane to these more manipulable vesicular systems will be characterized. The transport by bacteria of hexose-phosphates and Beta-galactosides in both energy coupled and uncoupled cells has been extensively characterized in my laboratory. These compounds are anionic and neutral, respectively, and hence, are well suited to be used as substrates in answering these questions. These measurements will provide excellent tests of the correlations between the proton motive force of the chemiosmotic theory and the transport of metabolites. Both whole cells and vesicle preparations (right-side-out and inside-out orientations) will be used where appropriate.